JP2009-287344A discloses a control system for hybrid construction machine including an electric motor which is rotated by power of a battery.
In this conventional system, a sub-pump is rotated by power of the electric motor which is rotated by the battery power and oil discharged from the sub-pump is introduced into a main pump to display an assist force.
When the storage amount of the battery decreases, the charging of the battery is prioritized by reducing the assist force of the sub-pump and increasing the rotation speed of the engine.